Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$235.66	6.354%	$250.6338	$250.63	$250.65	$250.60
Purchase #2	$246.73	3.849%	$256.2266	$256.23	$256.25	$256.20
Purchase #3	$105.95	5.652%	$111.9383	$111.94	$111.95	$111.90
Purchase #4	$170.88	13.819%	$194.4939	$194.49	$194.50	$194.50
Purchase #5	$84.74	6.745%	$90.4557	$90.46	$90.45	$90.50
Purchase #6	$21.42	10.111%	$23.5858	$23.59	$23.60	$23.60
Purchase #7	$219.56	8.218%	$237.6034	$237.60	$237.60	$237.60
7 purchase totals =	$1,084.94		$1,164.9375	$1,164.94	$1,165.00	$1,164.90